From mboxrd@z Thu Jan 1 00:00:00 1970 From: Avi Kivity Subject: Re: [patch 4/8] KVM: x86: replace hrtimer based timer emulation Date: Wed, 08 Jul 2009 16:41:22 +0300 Message-ID: <4A54A202.9080602@redhat.com> References: <20090706015511.923596553@localhost.localdomain> <20090706015812.786509491@localhost.localdomain> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Cc: kvm@vger.kernel.org To: Marcelo Tosatti Return-path: Received: from mx2.redhat.com ([66.187.237.31]:48704 "EHLO mx2.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753439AbZGHNiw (ORCPT ); Wed, 8 Jul 2009 09:38:52 -0400 Received: from int-mx2.corp.redhat.com (int-mx2.corp.redhat.com [172.16.27.26]) by mx2.redhat.com (8.13.8/8.13.8) with ESMTP id n68DcqpX004742 for ; Wed, 8 Jul 2009 09:38:52 -0400 In-Reply-To: <20090706015812.786509491@localhost.localdomain> Sender: kvm-owner@vger.kernel.org List-ID: On 07/06/2009 04:55 AM, Marcelo Tosatti wrote: > Replace hrtimer based timer emulation with host timebase (ktime_t) > comparisons on guest entry. > > This avoids host load when guests are scheduled out, removes a > spinlock acquision on entry (i8254.c's inject_lock), and makes future > improvements easier. > I wonder if we're really winning with this. Guests should be scheduled-out-but-not-halted rarely, and in all other cases we need to keep the timer. A timer comparison on each guest entry might be expensive (maybe not so much with tsc based timers). -- error compiling committee.c: too many arguments to function